Plasmonic light collectors

ABSTRACT

An electronic device may be provided with imaging modules or communications modules. Imaging modules and communications modules may be improved with the use of plasmonic light collectors. Plasmonic light collectors exploit the interaction between incoming light and plasmons in the plasmonic light collector to redirect the path of the incoming light. Plasmonic light collectors may be used to form lenses for image pixels in an imaging module or to form light pipes or lenses for use in injecting optical communications into a fiber optic cable. Plasmonic lenses may be formed by lithography of metallic surfaces, by implantation or by stacking and patterning of layers of materials having different dielectric properties. Plasmonic image pixels may be smaller and more efficient than conventional image pixels. Plasmonic light guides may have significantly less signal loss than conventional lenses and light guides.

This application is a division of patent application Ser. No.13/365,051, filed Feb. 2, 2012, which claims the benefit of provisionalpatent application No. 61/439,834, filed Feb. 4, 2011, and provisionalpatent application No. 61/529,584, filed Aug. 31, 2011 all of which arehereby incorporated b reference herein in their entireties. Thisapplication claims the benefit of and claims priority to patentapplication Ser. No. 13/365,051, filed Feb. 2, 2012, provisional patentapplication No. 61/439,834, tiled Feb. 4, 2011, and provisional patentapplication No. 61/529,584, filed Aug. 31, 2011.

BACKGROUND

This relates generally to electronic devices, and more particularly, toelectronic devices having plasmonic light collectors.

Plasmonic effects are quantum surface field effects in which anevanescent wave of election density oscillations is generated on or neara surface of a metal or meta-material in response to incident photons.In structures designed to exhibit plasmonic effects, incoming photonsincident on the plasmonic structure generate plasmons associated withhigh intensity electromagnetic fields within nano-scale distances fromthe surface of the structure. These high intensity electromagnetic,fields couple to the incoming photons and affect the path of travel ofthe photon near the plasmonic surface.

Plasmonic structures that affect visible light (i.e., light in thevisible part of the electromagnetic spectrum) require lithographicpatterning and material height differences on the surface of thestructures with dimensions of greater than 400 nanometers. Typicalsemiconductor volume manufacturing facilities lack such lithographycapabilities. These material height requirements have thereforerestricted the use of visible light plasmonic structures in electronicdevices such as imaging devices and communications devices.

It would therefore be desirable to be able to provide improved plasmonicstructures for use in imaging and communications devices.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of an illustrative electronic deice in accordancewith an embodiment of the present invention.

FIG. 2 is a cross-sectional side view of a conventional plasmonic lensfor use in plasmonic lens research.

FIG. 3A is a cross-sectional side view of a portion of an illustrativeimaging device having an array of plasmonic lenses in accordance with anembodiment of the present invention.

FIG. 3B is a top view of an illustrative imaging device such as theimaging device of FIG. 3A in accordance with an embodiment of thepresent invention.

FIG. 4 is a cross-sectional side view of an illustrative plasmonic lensformed by implantation in accordance with an embodiment of the presentinvention.

FIG. 5 is a cross-sectional side view of an illustrative plasmonic lensformed by layering alternating dielectric materials in accordance withan embodiment of the present invention.

FIG. 6 is a cross-sectional side view of an illustrative plasmonic lensformed from a vertical stack of materials in accordance with anembodiment of the present invention.

DETAILED DESCRIPTION

Electronic devices such as digital cameras, computers, cellulartelephones, or other electronic devices widely include imaging andcommunications modules. Imaging modules in these devices ma use one ormore lenses to focus incoming light onto corresponding image sensors inorder to capture a corresponding digital image. Communications modulesin these devices may use one or more lenses to focus incoming light intotransmission cables. Image sensors may include arrays of image sensorpixels. The pixels in the image sensors may include photosensitiveelements such as photodiodes that convert the incoming light intodigital data signals. Image sensors may have any number of pixels (e.g.,hundreds or thousands or more). A typical image sensor may, for example,have millions of pixels (e.g., megapixels). In high-end equipment, imagesensors with ten megapixels or more are not uncommon. Communicationsmodules in electronic devices may include light generating transmitterelements in addition to light focusing elements (lenses) designed todirect information encoded on electromagnetic waves (light) into acommunications cable.

FIG. 1 shows an electronic device in accordance with an embodiment ofthe present invention. As shown in FIG. 1, electronic device 10 mayinclude a communications module such as communications module 12 forgenerating an transmitting communications, an imaging module such asimaging module 20 for capturing an image, and processing circuitry 26for processing data and information captured, generated or received bycommunications module 12 or image module 20. Imaging module 20 may beconfigured to receive incoming image light 13 from an external object.Lenses in lens array 22 may be used to focus image light 13 onto aplasmonic light collector such as plasmonic light collectors 16.Plasmonic light collectors 16 may contain an array of image pixels thatcollect, filter and convert the image light into digital image data. Thedigital image data may be processed b processing and control circuitry26.

Circuitry 26 may be incorporated into imaging module 20 and/or may beimplemented using external processing, circuitry (e.g., amicroprocessor, an application-specific integrated circuit, etc.).Processing circuitry 26 may include one or more integrated circuits(e.g., image processing circuits, microprocessors, storage devices suchas random-access memory and non-volatile memory, etc.) and may beimplemented using components that are separate from imaging module 20and/or that form part or imaging module 20 (e.g., circuits that form panof an integrated circuit that includes plasmonic light collector 16 oran integrated circuit within module 20 that is associated with plasmoniclight collector 16). Image data that has been captured by imaging module12 may be processed and stored using processing circuitry 26. Processedimage data may, if desired, be provided to external equipment (e.g., acomputer or other device) using wired and/or wireless communicationspaths coupled to processing circuitry 26.

To provide plasmonic light collector 16 with the ability to detect lightof different colors, plasmonic light collector 16 may be provided with acolor filter array. Image pixels of plasmonic light collector 16 may beassociated with a pattern of color filter elements in which blueelements alternate with green elements in some rows and in which greenelements alternate with red elements in other rows. This is merelyillustrative. Plasmonic light collector 16 may, if desired, be agrayscale image sensor or alternatively or in addition to a color filterarray, plasmonic light collector 16 may be a color-sensitive imagesensor in which plasmonic image pixels may be individually configured topreferably accept a given color of light. Arrangements in whichplasmonic light collector 16 is a color-sensitive image sensor aresometimes described herein as an example.

As shown in FIG. 1, communications module 12 may include a lightgenerating transmitter module such as light generator 14 (sometimesreferred to herein as light generating module, light emitting module,transmitter, transmitting module, light transmitting module, etc.).Light generator 14 may, for example, include one or more alight-emitting diodes, laser transmitters or other optical transmitter.Communications module 12 may also include a plasmonic light collectorsuch as plasmonic light collectors 16. Plasmonic light collector 16 ofcommunications module 12 may be used to focus light generated usinglight generator 14 into a communications cable such as fiber optic cable18. Fiber optic cable 18 may be used couple communications module 12 toa communications network such as a local area network, a telephonenetwork, an interconnected network of computers, cable televisionnetwork, etc. Processing and control circuitry 26 may be used to controllight generator 14 of communications module 12 (i.e., to pass electricalsignals containing information to be converted into electromagneticsignals containing the information by light generator 14).

A conventional plasmonic lens that may be used in plasmonic lensresearch is shown in FIG. 2. As shown in FIG. 2, plasmonic lens 30receives incoming light 31. Plasmonic lens 30 helps concentrate light 31into opening 32 in plasmonic lens 30. Plasmons may be defined asoscillations of free electrons in a material such as a noble metal, adoped dielectric material or other material having free electrons.Surface plasmons occur at or near a surface at which a metal or othermaterial having a negative effective dielectric constant interfaces witha vacuum or other material having a positive dielectric constant. Atsuch an interfacing surface, evanescent waves of electrons are generateddue to the presence of incoming incident photons. Surface plasmonsresulting from the evanescent waves of electrons interact with theincoming photons and affect the path of travel of the incoming photons.Surface features may be designed on the surface of a metal at theinterface with a vacuum or other positive dielectric constant material)that purposefully guide photons such that the surface featureseffectively acts as a plasmonic lens (i.e., light waves are redirectedthrough openings in the plasmonic lens through interaction with surfaceplasmons).

As shown in FIG. 2, conventional plasmonic lens 30 is formed from apatterned metal such as metal layer 36 formed on a substrate such assubstrate 24 (e.g., a supporting structure formed from silicon). Surfacefeatures such as surface features 38 are typically configured to formconcentric rings surrounding opening 32 in plasmonic lens 36.Electromagnetic fields associated with plasmons generated near thesurface of metal layer 36 cause incoming light 31 to be redirected intoopening 32. Conventional plasmonic lenses have surface features 38having a typical height such as height H with a magnitude of less than10 nanometers and a width W (as shown in FIG. 2) of 50-200 nanometers.Current lithographic and etch procedures for producing surface featuressuch as surface features 38 limit the use of conventional plasmoniclenses such as lens 30 in communications and imaging modules ofelectronic devices. Incorporating plasmonic lenses into imaging modulessuch as imaging module 20 of device 10 ma include forming arrays ofplasmonic lenses and corresponding, image sensors as shown in FIG. 3A.

FIG. 3A is a cross-sectional side view of an imaging module such asimaging module 20 of electronic device 10 of FIG. 1. In the example ofFIG. 3A, lens array 22 may include one or more lenses 221 configured tofocus light on the plasmonic light collector 16. Plasmonic lightcollector 16 may include an array of plasmonic lenses such as plasmoniclenses 50. Plasmonic lenses 50 may be configured to focus light ontocorresponding image sensors such as image sensors 52. Each plasmoniclens 50 may have an associated color filter such as color filters 54.Plasmonic lenses 50 may be configured such that surface plasmonsresulting from evanescent waves of electrons generated by incomingphotons interact with the incoming photons and affect the path of travelof the incoming photons. Plasmonic lenses 50 may include a layer such aslayer 51 formed on substrate 53. Layer 51 may (as art example) include ametal layer formed on substrate 53. In the example in which layer 51includes a metal layer formed on substrate 53, layer 51 may includesurface features the surface of the layer 51 con figured to generateplasmons on the surface of layer 51 in response to light. Surfacefeatures may include one or more concentric rings on the surface oflayer 51 surrounding openings such as openings 56 in layer 51 ofplasmonic lens 50. The example in which layer 51 includes a metal layerhaving surface features is merely illustrative. Layer 51 may be formedfrom materials other than metal (e.g., silicon or other dielectric,meta-materials, etc.), may be formed from layers of materials ofdifferent dielectric constants, may be formed by implantation of amaterial having one dielectric constant into another material having adifferent dielectric constant or may be otherwise formed (e.g.,implanted, layered, patterned, etc.) such that, incoming photons areredirected into openings such as openings 56 in portions of plasmoniclenses 50. Plasmonic lenses may be configured to guide a light of asingle color (e.g., red light, blue light, green light, infrared light,x-ray wavelength light, ultra-violet light, etc.), a combination ofindividual colors, or wide continuous range of colors of light intoopenings 56.

In an array of numerous plasmonic lenses 50 and corresponding imagesensors 52, some of the image sensors may have red filters, some mayhave blue color filters, some may have green color filers, some may havepatterned ed color filters (e.g., Bayer pattern filters, etc.), some mayhave infrared-blocking filters, some may have ultraviolet light blockingfilters, some may be visible-light-blocking-and-infrared-passingfilters, etc. Plasmonic lenses 50 may be associated with combinations oftwo or more, three or more, or four or more of these filters or may havefilter of only one type. Image sensors 52 may include one or morephotosensitive elements such as photodiodes. In the example of FIG. 3A,incoming light is collected by the photodiode of image sensor 52 afterpassing through opening 56 in plasmonic lens 50 and, if desired, throughcolor filter 54. Incoming light may then be converted by the photodiodeinto electrical charge.

Image sensors 52 may include components such as reset transistors chargestorage nodes (also referred to as floating diffusion FD nodes) transfertransistors (transfer gates) or other components. Charge storage nodesmay be implemented using a region of doped semiconductor (e.g., a dopedsilicon region formed in a silicon substrate by ion implantation,impurity diffusion, or other doping techniques). The doped semiconductorregion (i.e., the floating diffusion FD) exhibits a capacitance that canbe used to store the charge that has been transferred from a piton:Rhodewhich has collected light that has passed through plasmonic lens 50. Thesignal associated with the stored charge on the floating diffusion node(sometimes referred to herein as image data) may be conveyed toprocessing and control circuitry 26 of electronic device 10 (see FIG. 1)through components such as row select transistors, source-followertransistors, or other components.

Image data that has been captured by imaging module 20 may be processedand stored using processing and control circuitry 26. Processed imagedata may, if desired, be provided to external equipment (e.g., acomputer or other device) using wired and/or wireless communicationspaths coupled to processing and control circuitry 26.

Image pixels 55 may be formed in an array of image pixels for imagingmodule 20. Each image pixel 55 may include a plasmonic lens such asplasmonic lens 50, an image sensor 52 and, if desired, a color filtersuch as color filter 54. Image pixels 55 may be separated by separatingstructures 57. Separating structures 5 i may be a disruptive implantformed from dielectric material such as silicon or other acceptablematerials that have been processed to form barriers between componentsof each pixel 55.

Plasmonic lenses such as plasmonic, lenses 50 of plasmonic lightcollector 16 have the advantage over conventional lenses that plasmonicstructures used to firm one plasmonic lens 50 may overlap plasmonicstructures used to form another plasmonic lens 50 without interference.FIG. 3B is a top-view of a plasmonic light collector such as plasmoniclight collector 16 of FIG. 3A. As shown in FIG. 3, plasmonic lenses 50may be formed from one or more concentric rings 60 surrounding opening56 in plasmonic lens 50. Concentric rings 60 may be formed fromlithographed or etched metal or other material, may be formed fromimplanted material having one dielectric constant in another materialhaving a different dielectric constant, or may be formed using othersuitable methods. Light having chosen frequencies (colors) may beallowed to pass through opening 56 in plasmonic lens 50 by adding moreor fewer rings having ring widths and ring diameters tuned to interactwith light of the chosen frequency. The example of FIG. 3B in whichplasmonic lenses 50 of plasmonic light collector 16 have concentricrinses of material is merely illustrative. Other structures such asstructures formed from layered materials in which alternating materialshave different dielectric constants may be used to form plasmonic lenses50.

As shown in FIG. 3B, plasmonic lenses 50 may be formed separately as inthe example of plasmonic lenses 50A and 50B or may be overlapping as inthe example of plasmonic lenses 50C and 50D.

FIG. 4 shows a cross-sectional side view of an illustrative plasmoniclens of the type that may be used in imaging module 20 of electronicdevice 10 of FIG. 1. In the example of FIG. 4, plasmonic lens 50 isformed using an implantation process (i.e., a process in which ions,noble metal atoms, other charged particles, or other suitable materialsare implanted in a layer of dielectric material having a positivedielectric constant in order to form regions having negative effectivedielectric constant in dielectric layer). As shown in FIG. 4, plasmoniclenses 50 may include a substrate support structure such as substratesupport structure 70. Substrate 70 may be formed from silicon, silicondioxide, sapphire, aluminum oxide, of other suitable materials.Plasmonic lens 50 may include a dielectric layer such as dielectriclayer 72. Dielectric laser 72 may be formed from ally suitabledielectric (e.g., nitride, polyimide or other suitable materials).Plasmonic structures such as plasmonic structures 74 may be formedwithin dielectric layer 72 using implantation methods in which a noblemetal (e.g., gold) or other material is implanted in dielectric layer 72in order to form regions of dielectric layer 72 having a negativeeffective dielectric constant (i.e., regions with metallic properties).As an example, dielectric layer 72 may be coated with a photo-resistivematerial and patterned using electron beam lithography before beingimplanted with a suitable material (e.g., gold, titanium oxide, or othermaterial) to form plasmonic structures 74 having a negative effectivedielectric constant.

Plasmons that interact with incoming light ma be formed at the interfacebetween any positive dielectric material and any negative effectivedielectric material. For this reason, changes in the local dielectricfunction produced by plasmonic structures 74 in plasmonic lens 50 mayproduce the same plasmonic lens properties of the lithographed plasmoniclens of FIG. 2. Plasmonic lens 50 may therefore be used in anyapplication for which plasmonic lens 30 of FIG. 2 may be used. Plasmoniclens 50, however, has the advantage that at least one process step(i.e., lithography of a metal layer to form nano-scale surface features)is not required. Replacing metal lithography with an implant process inthe formation of plasmonic lens 50 (as described in connection with FIG.4) may provide a variety of performance control options in constructingplasmonic structures 74 (e.g., control over shape, size, depth, etc. ofplasmonic structures 74). Plasmonic structures 74 may be formedsurrounding opening 56 in plasmonic lens 50. As an example, plasmonicstructures 74 may be configured to form concentric rings surroundingopening 56 in plasmonic lens 56 such that incoming light is guided (orfocused) into opening 56. Light that has been focused into opening 56may pass through substrate 70 and be collected by image sensor 52. Asdescribed in connection with FIG. 3A, image sensor 52 may include aphotosensitive element such as photodiode that converts incoming lightinto electrical charge. An electrical signal associated with theelectrical charge produced by the photodiode may be conveyed toprocessing and control circuitry 26 of electronic device 10 (see FIG. 1)through components such as row select transistors, source-followertransistors, or other components. Plasmonic lens 50 and image sensor 52may be combined to form a plasmonic image pixel such as plasmonic imagepixel 55. If desired, one or more plasmonic pixels 55 may be combined toform a plasmonic light collector such as plasmonic light collector 16 ofimaging module 20 of device 10. Two or more image pixels such as imagepixel 55 may be combined to form an array of image pixels for plasmoniclight collector 16. Image pixels 55 may be separated from neighboringimage pixels using separating structures 57. Separating structures 57may be formed from dielectric material such as silicon or otheracceptable materials that have been processed to firm electricalbarriers between components of each pixel 55.

FIG. 5 shows a cross-sectional side view of another illustrativeembodiment of a plasmonic lens of the type that may be used in imagingmodule 20 of electronic device 10 of FIG. 1. In the example of FIG. 5,plasmonic lens 50 is formed using layers of material having alternatingdielectric properties e.g., a vertical stack of two or more materials ora material stack with a variation in its dielectric properties due tocomposition or density). As shown in FIG. 5, plasmonic lenses 50 may beformed from two or more layers such as layers 80 and 82. If desired,layers 80 and 82 may be formed on the surface of substrate 70 in analternating stack. Layers 80 and 82 may have different dielectricproperties. For example, layer 80 may be a dielectric layer. Dielectriclayer 80 may be formed from any suitable dielectric (e.g., nitride,polyimide or other suitable materials). Layer 82 may be formed using anoble metal (e.g., gold) or may be formed from a layer of meta-materialdesigned to have a negative effective dielectric constant. Layers 80 and82 may be formed into a vertical stack by sequentially applying coatingsto substrate 70 (i.e., forming a coating of metal material 82 onsubstrate 70 followed by forming a coating of dielectric material $0 ontop of metal layer 82 followed by forming an additional coating of metalmaterial 82 on top of dielectric layer 80, etc., until the desired stackhas been formed). If desired, more than two layers of material havingmore than two corresponding effective dielectric constants may be usedto control and focus incoming light in a chosen manner (e.g., to allowlight of a chosen frequency to pass, to focus light on an image sensor.etc.).

As shown in FIG. 5, plasmonic lens 50 may be formed from material stack84 (including layers 80, 82 and it desired, other layers) along withsubstrate 70. Plasmonic lens 50 may have an opening such an opening 56.Layers 80 and 82 may be formed such that incoming light incident onplasmonic lens 50 is focused into opening 56 due to interaction of theincoming light with plasmons formed on inner surface 86 of opening 56.Plasmons formed at or near inner surface 86 of opening 56 (sometimesreferred to as plasmonic structure 86) may cause incoming light to passthrough substrate 70 and onto image sensor 52. Opening 56 may be formedin plasmonic lens 50 during a layering process (i.e., layers 80, 82 orother layers) may be screen printed or otherwise patterned ontosubstrate 70) such that opening 56 is left uncovered. In anotherexample, layers 80, 82, or other layers may be formed onto substrate 70and opening 56 may be opened later using a patterning method such as alithography, dry etch, wet etch, or other suitable process to form a viaor channel such as opening 56 having an (e.g., cylindrical) innersurface such as inner surface 86. Layers 80 and 82 may, if desired, beformed from a single material having regions with differing dielectricproperties due to differences in composition or density within thematerial. Opening 56 in a single material having regions with differingdielectric properties due to differences in composition or densitywithin the material may be formed using a patterning method such as alithography, dry etch, wet etch, or other suitable process to form a viaor channel such as opening 56 having a cylindrical inner surface such asinner surface 86.

As plasmons that interact with incoming light may be formed at theinterface between any positive dielectric material and any negativeeffective dielectric material, the changes in the local dielectricfunction produced by plasmonic structure 86 opening 56 of plasmonic lens50 may produce plasmonic lensing properties. Plasmonic lens 50, whenformed by layering (and, if desired, patterning one or more openings) ofmaterials such as materials 80 and 82, has the advantage that a processstep (i.e., lithography of a metal layer to form nano-scale surfacefeatures) is not required. Replacing metal lithography with verticalstacking process in the formation of plasmonic lens 50 (as described inconnection with FIG. 5) may provide a variety of performance controloptions in constructing plasmonic structures 86 (e.g., control overshape, size, depth, etc. of plasmonic structures 86). Inner surface 86may, for example, be substantially vertical (i.e., perpendicular to thesurface of substrate 70) as in 86-1, may be angled with respect to thesurface of substrate 70 as in 86-3, or may have curved surfaces havingchanging angles with respect to the surface of substrate 70 that changeas a function of distance from the surface of substrate 70 as in 86-2.Light that has been focused into opening 56 may pass through substrate70 and be collected by image sensor 52.

As described in connection with FIG. 3A, image sensor 52 may include aphotosensitive element such as photodiode that converts incoming lightinto electrical charge. An electrical signal associated with theelectrical charge produced by the photodiode may be conveyed toprocessing and control circuitry 26 of electronic device 10 (see FIG. 1)through components such as row select transistors, source-followertransistors, or other components. Plasmonic lens 50 and image sensor 52may be combined to form a plasmonic image pixel such as plasmonic imagepixel 55. If desired, one or more plasmonic pixels 55 may be combined toform a plasmonic light collector such as plasmonic light collector 46 ofimaging module 20 of device 10. Two or more image pixels such as imagepixel 55 may be combined to form an array of image pixels for plasmoniclight collector 16. Image pixels 55 may be separated from neighboringimage pixels using separating structures 57. Separating structures 57may be formed from dielectric material such as silicon or otheracceptable materials that have been processed to form electricalharriers between components of each pixel 55.

Plasmons formed on inner surface 86 of opening 56 may interact withlight that has entered opening 56 such that inner surface 86 functionsas a light pipe that redirects incoming light along opening 56 withoutpenetration of the electromagnetic fields of the light entering intolayers 80 or 82. This lack of penetration of electromagnetic fields intothe materials that form the inner surface of the light pipe may enhancethe efficiency with which light may be passed through opening 56 (i.e.,light will not be absorbed by materials 80 and 82 as the light nevercontacts materials 80 and 82).

FIG. 6 shows a cross-sectional side-view of an illustrativecommunications module such as communications module 12 of FIG. 1. Asshown in FIG. 6, communications module 12 may include a light generatingtransmitter module such as light generator 14 (sometimes referred toherein as light generating module, light emitting module, transmitter,transmitting module, light transmitting module. etc.), a plasmonic lightcollector such as plasmonic light collector 1.6 and a transmission cablesuch as fiber optic cable 18 in a housing such as housing 98.Transmitter 14 may, for example, include one or more a light-emittingdiodes, laser transmitters or other optical transmitters for generatedlight 90. Communications module 12 may also include a plasmonic lightcollector such as plasmonic light collector 16. Plasmonic lightcollector 16 of communications module 12 may be used to focus light 90generated using optical transmitter 14 into a communications cable suchas fiber optic cable 18. Fiber optic cable 18 may be used couplecommunications module 12 to a communications network such as a localarea network, a telephone network, an interconnected network ofcomputers, cable television network, etc.

Cable 18 may be formed from a core such as core 92. Core 92 may beformed from a transparent material such as silicon dioxide or othersuitable material. Core 92 of cable 18 may be surrounded by one or morewrapping layers such as layer 94. Layer 94 may include a dielectriclayer having an index of refraction lower than the index of refractionof core 94 so that light within cable 18 reflects within cable 18 due tothe principle of total internal reflection. Layer 94 may include otherlayers such as a plastic jacket (for example) to be used as a protectivehousing for cable 18. Cable 18 may be couple to plasmonic lightcollector 16 using an adhesive such as adhesive 96. Light 90 that hasbeen generated by transmitter 14 may be focused by plasmonic structure86 of plasmonic light collector 16 into cable 18 for transmission.Circuitry such as processing and control circuitry 26 of FIG. 1 may beused to encode information onto electromagnetic waves (light) fortransmission using transmitter 14, plasmonic light collector 16 andcable 18 of communications module 12 of device 10.

Plasmonic light collector 16 may be formed from material stack 84(including layers 80, 82 and, if desired, other layers). Plasmonic lightcollector 16 may have one or more openings such an opening 56. Layers 80and 82 may be formed such that incoming light incident on plasmoniclight collector 16 is focused into opening 56 due to interaction of theincoming light with plasmons formed on inner surface 86 of opening 56.Plasmons formed at or near inner surface 86 of opening 56 (sometimesreferred to as plasmonic structure 86) may cause incoming light to passthrough into cable 18. Opening 56 may be formed in plasmonic lens 50during a layering process (i.e., layers 80, 82 or other layers) may bescreen printed or otherwise patterned onto a temporary or permanentsubstrate) such that opening 56 is left uncovered. In another example,layers 80, 82, or other layers may be formed onto a temporary orpermanent substrate and opening 56 may be opened later using apatterning method such as a lithography, dry etch, wet etch, or othersuitable process to form a via or channel such as opening 56 having an(e.g., cylindrical) inner surface such as inner surface 86. Layers 80and 82 may, if desired, be formed from a single material having regionswith differing dielectric properties due to differences in compositionor density within the material. Opening 56 in a single material havingregions with differing dielectric properties due to differences incomposition or density within the material may be formed using apatterning method such as a lithography, dry etch, wet etch, or othersuitable process to form a via or channel such as opening 56 having an(e.g., cylindrical) inner surface such as inner surface 86.

As plasmons that interact with incoming light may be formed at theinterface between any positive dielectric material and any negativeeffective dielectric material, changes in the local dielectric functionproduced by layers 80 and 82 of plasmonic structure 86 in opening 56 mayproduce plasmonic lensing properties. Replacing conventional lenses orlight pipes with plasmonic light collectors formed using a verticalstacking process may provide a variety of performance control options inconstructing plasmonic structures 86 (e.g., control over shape, size,depth, etc. of plasmonic structures 86). Inner surface 86 may, forexample, be substantially vertical (i.e., perpendicular to the surfaceof substrate 70) as in 86-1, may be angled with respect to the surfaceof substrate 70 as in 86-3, or may have curved surfaces having changingangles with respect to the surface of substrate 70 that change as afunction of distance from the surface of substrate 70 as in 86-2. Theproperties of plasmonic structure 86 may be chosen such that interactionbetween plasmons on plasmonic structure 86 and incoming light 90 limitsthe bandwidth (i.e., the range of frequencies) of transmission acceptedinto cable 18. By choosing the properties of plasmonic structure 86 tolimit the bandwidth (i.e., the range of frequencies) of transmissionaccepted into cable 18, plasmonic light collector 16 may be utilized asa color filter (i.e., multiple plasmonic light collectors havingdifferent arrangements or stacking thicknesses of layers 80 and 82 ofplasmonic structure 86 may provide multiple color filters fortransmission into cables such as cable 18).

Various embodiments have been described illustrating electronic deviceswith imaging modules and/or communications modules having plasmoniclight collectors. Plasmonic light collectors may be configured toexploit the interaction between incoming light and plasmons generated ona surface of the plasmonic light collector to redirect the path of theincoming light. Redirecting the incoming light may include focusing thelight through openings in the plasmonic light collector onto lightabsorbing components such as image sensors, fiber optic transmissioncables or other components. Plasmonic light collectors may be used toform plasmonic lenses associated with image pixels in an imaging moduleor to form plasmonic light pipes or plasmonic lenses for use ininjecting or transmitting optical communications generated by atransmitter into a fiber optic cable. Plasmonic lenses may be formed bylithography of metallic surfaces, by implantation of negative dielectricconstant materials into a dielectric or by stacking and patterninglayers of materials having different dielectric properties such aspositive and negative effective dielectric constants. Plasmonic imagepixels may be smaller and more efficient than conventional image pixels.Plasmonic light guides may introduce light into transmission cables withsignificantly less signal loss than conventional lenses and lightguides.

The foregoing is merely illustrative of the principles of this inventionwhich can be practiced in other embodiments.

What is claimed is:
 1. A plasmonic light collector for guiding lightinto a transmission cable through an opening in the plasmonic lightcollector, comprising: a first dielectric layer, wherein the firstdielectric layer has a positive dielectric constant; a first negativeeffective dielectric constant layer formed on the first dielectriclayer, wherein the first negative effective dielectric constant layerhas a negative effective dielectric constant, wherein the openingcomprises an opening in the first dielectric layer and the firstnegative effective dielectric layer, and wherein the opening isconfigured to guide the light into the transmission cable using aninteraction between the light and plasmons associated with the opening;a second dielectric layer formed on the first negative effectivedielectric constant layer, wherein the second dielectric layer has apositive dielectric constant; and a second negative effective dielectricconstant layer formed on the second dielectric layer, wherein the secondnegative effective dielectric constant layer has a negative effectivedielectric constant, and wherein the opening further comprises anopening in the second dielectric layer and the second negative effectivedielectric layer.
 2. The plasmonic light collector defined in claim 1wherein the first and second dielectric layers comprise silicon.
 3. Theplasmonic light collector defined in claim 1 wherein the first andsecond negative effective dielectric constant layers comprise gold. 4.The plasmonic light collector defined in claim 1 wherein thetransmission cable is connected to the plasmonic light collector byadhesive.
 5. The plasmonic light collector defined in claim 1, whereinthe plasmonic light collector is coupled to a transmitter configured togenerate the light and wherein the plasmonic light collector isconfigured to focus the light generated by the transmitter into thetransmission cable.
 6. The plasmonic light collector defined in claim 5,wherein the transmission cable comprises a fiber optic transmissioncable having an inner core layer surrounded by a wrapping layer, andwherein the plasmonic light collector is configured to focus the lightgenerated by the transmitter into the core layer of the fiber optictransmission cable.
 7. The plasmonic light collector defined in claim 1,wherein the first dielectric layer, the second dielectric layer, thefirst negative effective dielectric constant layer, and the secondnegative effective dielectric constant layer are configured to filterout a range of frequencies of the light that is guided into thetransmission cable.
 8. The plasmonic light collector defined in claim 1,wherein the first dielectric layer has a planar surface and wherein theopening in the first dielectric layer, the second dielectric layer, thefirst negative effective dielectric constant layer, and the secondnegative effective dielectric constant layer has an inner surface thatis substantially perpendicular to the planar surface of the firstdielectric layer.
 9. The plasmonic light collector defined in claim 1,wherein the first dielectric layer has a planar surface and wherein theopening in the first dielectric layer, the second dielectric layer, thefirst negative effective dielectric constant layer, and the secondnegative effective dielectric constant layer has a curved inner surface,wherein the curved inner surface has an angle that changes with respectto the planar surface as a function of distance from the planar surface.10. An electronic device, comprising: a transmission cable; and a lightcollector, wherein the light collector comprises a first region having apositive dielectric constant, a second region having a negativeeffective dielectric constant, a third region having a positivedielectric constant, a fourth region having a negative effectivedielectric constant, wherein the third region is interposed between thesecond and fourth regions, wherein the light collector is configured toredirect light incident on the light collector onto the transmissioncable using an interaction between the incident light and plasmonsgenerated on a surface of the light collector by the incident light. 11.The electronic device defined in claim 10, wherein the plasmons aregenerated at at least one of an interface between the third and fourthregions and an interface between the first and second regions.
 12. Theelectronic device defined in claim 11, wherein the light collector isconfigured to redirect the incident light onto the transmission cablethrough an opening in the first, second, third, and fourth regions. 13.The electronic device defined in claim 12, wherein the first region isformed from a given material, wherein the first region has a firstdensity, wherein the second region is formed from the given material,and wherein the second region has a second density that is differentfrom the first density.
 14. The electronic device defined in claim 12,wherein the first region comprises a first dielectric layer, wherein thesecond region comprises a second dielectric layer, wherein the thirdregion comprises a third dielectric layer, wherein the fourth regioncomprises a fourth dielectric layer, wherein the first dielectric layeris formed over the second dielectric layer, wherein the fourthdielectric layer is formed on the third dielectric layer, and whereinthe opening is formed in the first, second, third, and fourth dielectriclayers.
 15. The electronic device defined in claim 12, wherein the thirdregion is formed from a first material, wherein the third region has afirst density, wherein the fourth region is formed from a secondmaterial, and wherein the fourth region has a second density that isdifferent from the first density.
 16. The electronic device defined inclaim 12, wherein the transmission cable comprises a fiber optictransmission cable having a core layer and a wrapping layer, wherein thelight collector comprises a plasmonic light collector, and wherein theplasmonic light collector is configured to redirect the incident lightthrough the opening onto the core layer of the fiber optic transmissioncable.
 17. A system, comprising: a central processing unit; memory;input-output circuitry; an optical light source configured to generatelight; a fiber optic cable; and a plasmonic light collector, comprising:a first dielectric layer having a positive dielectric constant; and asecond dielectric layer having a negative effective dielectric constant;a third dielectric layer having a positive dielectric constant; and afourth dielectric layer having a negative effective dielectric constant,wherein an opening is formed in the first, second, third, and fourthdielectric layers, and wherein the plasmonic light collector isconfigured to guide the light generated by the optical light source ontothe fiber optic cable through the opening using an interaction betweenthe light and plasmons generated by the light at at least one of aninterface between the first and second dielectric layers and aninterface between the third and fourth dielectric layers.
 18. The systemdefined in claim 17, wherein the optical light source comprises a lightsource selected from the group consisting of: a light-emitting diode anda laser.
 19. The system defined in claim 18, further comprising:processing circuitry, wherein the processing circuitry is configured toencode information onto the light generated by the optical light source.